Why and how we age

Time of Our Lives

• Thomas B Kirkwood

Weidenfeld & Nicolson, The Orion Publishing Group, $20,, 1999 ISBN 0-297-84247-1 | ISBN: 0-297-84247-1

There has been a recent acceleration in the rate of publication of books on the biology of ageing by gerontological colleagues. A number of these have been designed for a rather general readership, for which I am grateful, as these have served to immunize me against the temptation to write yet another popular book on ageing. Among the latest offerings is Time of Our Lives , by Thomas B. Kirkwood, who is a leading biogerontologist in the UK and the first to hold a Chair of Biological Gerontology (at the University of Manchester). Kirkwood is exceptionally well read and well informed in all aspects of gerontology, including social gerontology and geriatrics (the medical branch of gerontology). He therefore has produced what I would have expected: a thoroughly charming and delightful narrative. Moreover, despite his efforts to simplify via the liberal use of metaphors and anecdotes, he has managed to present what is—by and large—a quite accurate picture of the state of the art.

Kirkwood developed his interests in the biology of ageing in the late 1970s under the tutelage of Robin Holliday, the distinguished geneticist best known for his early work on the nature of molecular intermediates in genetic recombination ('Holliday junctions'). Kirkwood's early work dealt with models to explain the clonal attenuation of normal diploid human cells in culture, but his major contribution has been the articulation of the 'disposable soma' theory of why we age. This is, in essence, an application of the evolutionary biological tradeoff concept to the genesis of senescence, with a specific emphasis on energetics. Given highly hazardous ecological niches, there is strong selective pressure to get the job of reproduction done quickly, and there is no point in diverting resources to better maintenance of macromolecular integrity. Hence, senescence develops rapidly. But Nature has proven itself capable of doing a much better job of keeping our soma together for long periods of time when given more benign environments over sufficiently long periods of time. This intrinsic plasticity of life span is the good news about the biology of ageing. The bad news is that it is hard to distil hundreds of years of evolution into a pill or a single gene.

I learned from Time of Our Lives that the author conceived the disposable soma concept before coming across the seminal publication by George W. Williams (Pleiotrophy, natural selection, and the evolution of senescence. Evolution 11, 398–411; 1957), whose ideas were comparable to those of Kirkwood. Kirkwood also pays homage to other major contributors to the evolutionary biological theory of ageing, particularly Peter Medawar and William Hamilton. It is thus not surprising that by far the best feature of this book is the explication of these ideas about why we age. (The same is true of Steven N. Austad's Why We Age: What Science Is Discovering about the Body's Journey Through Life and Michael R. Rose's Evolutionary Biology of Ageing.) Cell and molecular biologists might therefore wish to read Time of Our Lives for only that reason. They will find themselves rapidly turning the pages of the superficial review of relevant basic science, as this material is packaged for the intelligent general public. One should not be misled by the book jacket text, which announces that Kirkwood not only tells us why we age, but also tells us "precisely" how we age. Kirkwood, like others before him, cannot reveal all the truths about the proximal mechanisms of ageing because these are the subjects of ongoing research. And as he points out, evolutionary biological theory predicts that there should be a number of different mechanisms of ageing.

One can quibble about some highly speculative extrapolations from current scientific evidence, but no serious violence is done to the public consumers of scientific information on the biology of ageing. The author's suggestion that exercise may help select against the over-representation of mutant mitochondrial DNA in our skeletal muscles is one such example. But there is some evidence that moderate exercise does us a lot of good; laymen do not have to worry about underlying mechanisms.

I am often asked by non-biologists if I can recommend a good book to inform them about the nature of ageing and what, if anything, can be done about it. Time of Our Lives is the one I would now recommend, as it deals intelligently with most of their questions—from genes to vitamins. I will not reveal to them (or to the readers of Nature Genetics) the secret of his epilogue, however, except for this clue: it suggests that the next book by Tom Kirkwood is going to be a wonderful piece of science fiction. I hope it will arrive just in time to serve as a booster shot to enhance my immunization against writing a popular book about ageing!boxed-text

Box 1: The art of ageing

Bearing the same title as the book above, an art exhibition at the New Museum of Contemporary Art, New York, explores the ageing process from a different perspective. A collection of images portrayed through a diverse array of media "expose ageist ideas and practices" common to western society. The use of modern technology in much of the artwork—including holographic imaging of a nude elderly woman—conveys powerful depictions of how body, attitude and technology change during a lifetime. The connections made between ageing, chemistry and art are occasionally treated with humour, such as an installation that abstractly portrays the breakdown of the crystalline matrix of bone and the content of an aged person's refrigerator. Many of the installations were created by young people or are accompanied by wall texts expressing a young person's perception of the image, and illustrate that many young people do not share the derogatory attitudes toward ageing that are frequently conveyed in western media. Nevertheless, the intent to deconstruct negative views of ageing results in a narrow perception of the subject. Although it captures the optimism of many individuals entering their 'twilight' years, the exhibition fails to meaningfully express the fragility, frustration and isolation that one senses from the subcontext of some of the images.

—Carina Dennis